Statement of Principles concerning popliteal entrapment syndrome (Reasonable Hypothesis) (No. 54 of 2017)

Popliteal entrapment syndrome is defined in subsection 6(2) as an acquired or congenital, partial or complete occlusion of the popliteal artery in the popliteal fossa that occurs during plantar flexion, in the presence of symptoms of intermittent lower limb claudication, exercise-induced leg pain, paraesthesia, or lower limb ischaemia, and in the absence of other identifiable vascular risk factors that can account for those symptoms. The definition also requires appropriate clinical imaging studies that confirm the partial or complete occlusion. The note lists examples of imaging modalities: Doppler ultrasonography, static or dynamic MRI/MRA, CT angiography, conventional catheter-based angiography with provocation, and intravascular ultrasound. The definition excludes cases where other vascular risk factors are present and can independently explain the symptoms, which means the diagnosis must be one of exclusion to some degree.

The concept of "clinical onset" is not defined in the instrument but is used in factors 8(1)-(4) to refer to the first manifestation of symptoms meeting the diagnostic criteria. "Clinical worsening" is used in factors 8(5)-(9) and, under the note, applies only to material contribution to or aggravation of a pre-existing PES that was suffered or contracted before or during (but did not arise out of) relevant service. This distinction is critical: a person whose PES first manifested during service can rely on the onset factors, while a person whose PES existed before service and was worsened by service must meet the stricter worsening factors and must also satisfy the relationship provision in section 9(2).

A central concept is the metabolic equivalent of task (MET). The Schedule defines 1 MET as 3.5 ml of oxygen per kg of body weight per minute, 1.0 kcal per kg per hour, or resting metabolic rate. Factors 8(2) and 8(6) require that the vigorous physical activity be at a minimum intensity of six METs. This is a quantifiable threshold: activities above six METs include jogging (typically 7 METs), cycling at moderate effort (8 METs), heavy vehicle driving may involve sustained isometric contractions that can exceed six METs, martial arts (8-10 METs), rugby, soccer, basketball, rowing, and similar. The RMA's note expressly lists driving heavy vehicles as an example, which is notable because it can apply to non-athletic occupations.

"Relevant service" is defined in the Schedule to include operational service, peacekeeping service, hazardous service, and British nuclear test defence service under the VEA, as well as warlike and non-warlike service under the MRCA. This defines the class of persons to whom the SoP applies. The concept of "terminal event" is also defined in the Schedule to cover proximate or ultimate causes of death such as pneumonia, respiratory failure, cardiac arrest, circulatory failure, or cessation of brain function, where that event was contributed to by PES.

"Disease involving the popliteal fossa" means any pathological condition causing anatomical distortion of the popliteal fossa. The note gives examples: a primary or secondary neoplasm within the knee joint or long bones of the leg, or a popliteal (Baker's) cyst. This is a broad definition that could encompass a range of conditions, so claimants must demonstrate that the disease caused anatomical distortion.

The instrument directly affects three classes of people: claimants (veterans, members of Peacekeeping Forces, members of the Forces under the VEA, and members under the MRCA) who seek compensation for PES or death from PES; decision-makers in the Department of Veterans' Affairs and the Military Rehabilitation and Compensation Commission who assess claims; and medical practitioners who provide evidence and opinions in support of claims. The instrument also indirectly affects employers of defence personnel, insurers, and veterans' advocacy organisations, because it sets the evidentiary benchmark for entitlement.

For claimants, the instrument imposes a burden of proof at the reasonable hypothesis standard. They must submit medical evidence showing a diagnosis of PES that meets the definition in section 6, and factual evidence showing that at least one factor in section 8 exists and is related to relevant service. The thresholds are precise: 20 km per week of running for six months, or 20 hours per week of activities at six METs for six months, or trauma within five years, or a disease causing anatomical distortion at the time of onset. A claimant who cannot produce records or credible testimony of those activity levels will struggle to raise a reasonable hypothesis. This particularly affects older veterans who may not have maintained activity logs, or those whose military service involved standing duties rather than repeated plantar flexion. The instrument excludes from the definition of PES cases where other vascular risk factors explain the symptoms, which may disadvantage claimants with diabetes, hypertension, or hyperlipidaemia who also have PES , they must show that those risk factors do not account for the symptoms.

For decision-makers, the instrument provides a structured checklist. They must first confirm the diagnosis meets the definition, then determine whether the claimed factor exists, then relate it to service. The notes under section 8 give examples of vigorous physical activities, which help standardise assessment but also create a risk of over-inclusion if decision-makers rely too heavily on the examples rather than the MET threshold. The requirement that clinical worsening factors apply only to material contribution or aggravation (section 9(2)) means that decision-makers must distinguish between mere progression of a pre-existing condition and service-related worsening.

Medical practitioners are affected because their reports must address the specific factor thresholds: the patient's running kilometres per week, MET intensity, hours per week of activity, or evidence of trauma or disease. The imaging requirements in section 6(2)(b) mean that a diagnosis without appropriate imaging (Doppler, MRI/MRA, CT angiography, etc.) may not satisfy the definition. Practitioners must also exclude other vascular risk factors, which may require additional testing. The instrument thus increases the evidentiary demands on clinicians compared to a more discretionary system.

The instrument creates no direct duties or rights, but it operates within the framework of the VEA and MRCA, which impose duties on the Commonwealth to pay compensation to eligible persons. The key duty relevant here is the decision-maker's duty under section 120A of the VEA and section 338 of the MRCA to determine whether a reasonable hypothesis exists connecting the injury or disease to service. This instrument binds the decision-maker: if at least one factor in section 8 is satisfied and related to service, the decision-maker must find that a reasonable hypothesis has been raised. Conversely, if no factor is satisfied, the decision-maker must find that a reasonable hypothesis has not been raised, and the claim must fail unless the claimant can rely on another SoP or a direct relationship without an SoP (which is extremely limited under the legislation).

Claimants have the right to present evidence that meets one or more of the factors. They also have the right to rely on the instrument itself: the instrument is determinative, not merely advisory. If a factor is made out, the decision-maker cannot reject the hypothesis on the basis of insufficient medical plausibility unless the factor itself is not related to service or the definition of PES is not met. The instrument also creates a right of consistency: all claims for PES are assessed using the same set of factors, reducing individual decision-maker discretion.

The RMA has a duty under section 196B(2) of the VEA to determine SoPs based on sound medical-scientific evidence. The instrument states that the RMA is of the view that such evidence exists for PES. This view is not subject to merits review, but the instrument can be challenged if the RMA acted beyond power or failed to take into account relevant considerations.

For claimants, the instrument also imposes a de facto duty to keep records of physical activity levels if they intend to claim later. This is a practical compliance burden: a veteran who ran 20 km per week for six months but cannot prove it with credible evidence (e.g., training logs, unit records, medical records of injuries) may not meet the factor. Similarly, a claimant relying on the trauma factor (subsection 8(3) or (7)) must show that trauma to the affected limb involved the popliteal fossa and displaced the popliteal artery. This requires medical imaging evidence at the time of trauma or a clear causal chain, not merely a history of blunt trauma.

This instrument does not itself create penalties. It is not a regulatory instrument that prohibits conduct or imposes fines. Its enforcement is indirect: if a claimant fails to satisfy the factors, the decision-maker will reject the claim for compensation, which is a denial of a benefit rather than a penalty. The real risk for claimants is the loss of compensation payments, medical treatment entitlements, and potentially war widow's pension. For medical practitioners who provide reports that do not address the factors, the consequence is that the claim may fail, and the practitioner may face reputational or professional criticism from tribunals or courts if the evidence is found to be inadequate.

The instrument can affect the enforcement of other laws. For example, under the VEA and MRCA, there are provisions for criminal penalties for fraud (e.g., making false statements in support of a claim). A claimant who fabricates evidence of running distance or MET activity to meet a factor could face prosecution under the Criminal Code. The SoP thus raises the stakes: the more precise the factor, the easier it is to detect fraudulent claims if records are checked, but also the easier it is for a genuine claimant to fail due to lack of perfect records.

There is no mechanism for the RMA to enforce compliance with the SoP beyond its own determinations. The instrument does not impose obligations on third parties such as employers or medical facilities. However, if a decision-maker fails to apply the SoP correctly, the claimant can seek review by the Veterans' Review Board and then the Administrative Appeals Tribunal (AAT), and ultimately the Federal Court on a question of law. An incorrect application that denies a benefit could lead to an order to reconsider the claim with proper application of the SoP. That is the only enforcement remedy available to a claimant.

The instrument is made under subsection 196B(2) of the VEA and applies to claims to which section 120A of the VEA or section 338 of the MRCA applies. Section 120A VEA provides that the reasonable hypothesis standard applies to claims relating to operational service, peacekeeping service, hazardous service, and British nuclear test defence service. Section 338 MRCA contains the equivalent for warlike and non-warlike service under that Act. The SoP does not apply to claims where the standard is balance of probabilities, such as non-operational service under the VEA or some MRCA claims that are not subject to section 338. This is a critical interaction: a veteran who rendered only peacetime (non-operational) service under the VEA cannot rely on this SoP because the reasonable hypothesis standard does not apply to such claims; instead the claim would be assessed under the balance of probabilities standard, and the SoP is merely one piece of evidence rather than determinative.

The instrument also interacts with other SoPs. Section 10 provides that if a factor in section 8 refers to an injury or disease for which a different SoP has been determined (e.g., trauma to the popliteal fossa may involve a fracture or soft tissue injury covered by a separate SoP), then the factors in that other SoP apply in accordance with its terms as in force from time to time. This creates a cross-reference mechanism: to establish the trauma factor in subsection 8(3), the claimant may need to show that the trauma itself is related to service, and that may require satisfying a different SoP if the nature of the trauma is itself a condition covered by a SoP (e.g., fractures). This can add complexity where multiple SoPs are applicable to different factual elements.

The instrument interacts with the VEA's definition of "injury" and "disease" and with the concepts of "clinical onset" and "clinical worsening" as used in other SoPs. There is an established body of case law from the AAT and Federal Court interpreting those terms, though the instrument does not refer to any cases. Consistency across SoPs is maintained because the RMA uses uniform definitions where possible (e.g., "terminal event", "MET", "relevant service").

The instrument also interacts with state and territory workers' compensation schemes, though not directly. A veteran who is also a civilian employee may have a claim under state law for PES. The SoP has no legal effect on those schemes, but in practice, treating doctors may use the same factor thresholds in civilian medico-legal reports, creating a spill-over effect.

This instrument, No. 54 of 2017, is a stand-alone determination by the RMA. It has no stated amendment history within its text. It was made on 18 August 2017 and commenced on 18 September 2017. It replaced any earlier SoP on popliteal entrapment syndrome, but the source does not identify a prior number or date. The instrument does not list amendments or earlier versions. The RMA may have previously determined a SoP on this condition under the same legislative power, and if so, this instrument revoked that earlier SoP by operation of law (an earlier SoP is impliedly repealed when a new one on the same condition is made). However, the instrument does not say it revokes anything, which is standard for RMA SoPs: each new SoP for a condition is independent, and claims assessed after its commencement are determined under the new SoP.

The instrument can be amended by a later SoP. The RMA may issue a new SoP on PES at any time if it reviews the medical evidence. The note in section 10 refers to Statements of Principles determined under subsection 196B(2) "as in force from time to time", which confirms that the RMA treats its own SoPs as dynamic. However, this instrument itself has not been amended since its commencement, based on the source provided. Practitioners must check the Federal Register of Legislation for any later SoP that revokes or replaces No. 54 of 2017.

The instrument does not record any consultation history or explanatory memorandum, but such documents are typically prepared by the RMA and published separately. The instrument is a legislative instrument subject to disallowance by Parliament, but there is no evidence in the source of any disallowance motion.

The instrument itself has not been the subject of litigation disclosed in the source. The source does not name any cases. However, the reasonable hypothesis standard under the VEA has been extensively litigated in the Federal Court and High Court, and the interpretation of SoPs generally has been considered in decisions such as Repatriation Commission v Deledio (1998) 83 FCR 82 and later cases. Those cases establish the four-step test for applying a SoP: (1) identify the SoP that applies; (2) determine whether the hypothesis fits the template of the SoP (i.e., is the factor met?); (3) if yes, proceed to consider the material before the decision-maker; (4) decide whether the hypothesis is reasonable. This framework is not mentioned in the instrument but is settled law.

A specific challenge to this SoP could be mounted on grounds that the RMA failed to base it on sound medical-scientific evidence, but that would require judicial review for jurisdictional error. No such case is known from the source. The definition of PES in subsection 6(2) requires the absence of other identifiable vascular risk factors, which could give rise to disputes about what counts as "identifiable" and whether a risk factor that is present but not causative excludes the syndrome. The notes and definitions may be tested in the AAT on a case-by-case basis. The factor thresholds (20 km per week, 6 METs, 20 hours per week) are precise and may be contested on the basis that the evidence does not support a causal link at those levels, but the RMA's view is given weight by tribunals and courts, so that challenge is unlikely to succeed unless new evidence emerges.

There is a risk that the AAT or Federal Court will read down the definition of "disease involving the popliteal fossa" or "trauma to the affected limb" if they consider the RMA has gone beyond its powers, but no such litigation is evident from the source.

Several provisions in the instrument create traps for the unwary claimant. First, the definition of popliteal entrapment syndrome in subsection 6(2) requires that the occlusion occurs during plantar flexion. If the imaging studies are performed only in a neutral position and show no occlusion, the diagnosis may not be accepted even if the patient has symptoms. Dynamic imaging is essential. Second, the definition also requires "appropriate clinical imaging studies" that confirm partial or complete occlusion. The note lists five modalities, but this is not exhaustive; however, a doctor's report that does not specify which imaging was used and fails to confirm occlusion to the decision-maker's satisfaction may mean the condition itself is not established.

Third, the requirement that there be "no other identifiable vascular risk factors that can account for those symptoms" can be a severe hurdle. A claimant with hypertension, diabetes, or hyperlipidaemia who also suffers from claudication must show that those factors do not account for the symptoms, which may require additional testing (e.g., ankle-brachial indices, duplex ultrasound) to exclude atherosclerotic disease. If the decision-maker considers that the symptoms could be explained by those risk factors, the PES diagnosis may not be accepted, and the claim fails even if the SoP factors exist.

Fourth, the running thresholds are specific: 20 km per week for six months before clinical onset (subsection 8(1)), and 10 km per week for three months before clinical worsening (subsection 8(5)). The difference between onset and worsening is a trap: a claimant whose PES was first diagnosed after service and who had been running 15 km per week for three months before diagnosis cannot satisfy the onset factor (needs 20 km per week) and likely cannot satisfy the worsening factor because there was no worsening of a pre-existing condition , it was the onset. The claimant must show either a higher running volume or rely on another factor.

Fifth, the vigorous physical activity factor in subsections 8(2) and 8(6) requires "repeated active plantar flexion" or "repetitive sudden and forceful contraction of the calf" at an average of at least 20 hours per week for a continuous period of at least six or three months. A claimant who does mixed activities (e.g., two hours of running per week, plus weights, but not predominantly plantar flexion) may not meet the MET threshold or the activity type. The note lists "driving heavy vehicles" as an example, which is surprising because it is not obviously a high-MET activity; but the RMA includes it, likely because sustained pressure on the clutch or brake pedal can involve repeated plantar flexion. A claimant who drives a heavy vehicle for 40 hours per week but does no other exercise may still meet the factor if the MET intensity is verified.

Sixth, the trauma factor (subsections 8(3) and 8(7)) requires that the trauma be to the affected limb, involve the popliteal fossa, and displace the popliteal artery, within five years before the clinical onset or worsening. A simple bruise or sprain that does not displace the artery will not suffice. The claimant must show imaging or surgical evidence of displacement. This is a narrow factor.

Seventh, the clinical worsening factors in subsections 8(5)-(9) apply only where the PES was suffered or contracted before or during (but did not arise out of) relevant service (section 9(2)). That means if the onset of PES occurred during service and is related to service (i.e., it arose out of service), the worsening factors are irrelevant because the condition is already compensable. But if the onset occurred before service and was aggravated by service, the worsening factors must be satisfied and related to service. This creates a factual inquiry into when the condition first manifested, which may be difficult to determine if symptoms were mild.

Eighth, the "inability to obtain appropriate clinical management" factor (subsection 8(9)) is a residual factor that could apply in cases where the service prevented the person from getting timely treatment, but the instrument does not define what constitutes inability or appropriate management. This leaves discretion to the decision-maker.

Compliance with this instrument is relevant to claimants and their representatives in preparing a claim, and to decision-makers in assessing it. For a claimant, the first step is to obtain a firm diagnosis of popliteal entrapment syndrome that meets the definition in section 6. That means a specialist vascular surgeon or sports medicine physician should perform dynamic imaging (e.g., Doppler ultrasound with plantar flexion) and produce a report that states: (1) there is partial or complete occlusion of the popliteal artery during plantar flexion; (2) the patient has symptoms of claudication, exercise-induced leg pain, paraesthesia, or ischaemia; and (3) there are no other identifiable vascular risk factors that can account for the symptoms (or those that exist are not causative). The report should exclude atherosclerosis, thrombosis from other causes, and other conditions.

Second, the claimant must identify which factor in section 8 applies and gather corroborating evidence. For the running factors, evidence can include running logs (diaries, GPS data, race results), gym attendance records, unit physical training records for military service, or statements from witnesses who observed the running schedule. The period must be continuous for the specified duration: "for the six months before the clinical onset" or "for the three months before the clinical worsening". The clinical onset date must be established, usually from medical records showing the first consultation for symptoms. For the vigorous physical activity factor, the claimant should record the type of activity, the hours per week, and the MET intensity. The RMA's note gives examples, but a claimant relying on heavy vehicle driving should obtain an occupational therapy assessment of MET output during driving. For the trauma factor, the claimant must produce medical records (hospital, GP, or specialist) showing the trauma, its location (popliteal fossa), and imaging that confirms displacement of the popliteal artery. This may require retrospective arteriography if not done at the time. For the disease factor, a diagnosis of a condition such as Baker's cyst or tumour must be shown to cause anatomical distortion of the popliteal fossa; imaging is again essential.

Third, the claimant must show that the chosen factor is related to relevant service. This may be straightforward if the running or vigorous activity was undertaken in the course of military duties or training, but if the activity was off-duty and purely recreational, the decision-maker must consider whether it is related. The instrument says the factor must be "related to the relevant service rendered by the person" (section 9(1)). The VEA case law interprets "related to service" broadly, but the claimant should provide evidence that the activity was part of, or influenced by, service (e.g., mandatory physical training, operational deployments requiring long drives, combat training with running). For the trauma factor, the trauma must have occurred during service. For the disease factor, the disease must have been present during service.

Fourth, if the claim is for worsening of a pre-existing condition, the claimant must establish that the condition existed before the relevant service and that the worsening occurred due to service factors. The date of clinical worsening must be identified (e.g., when symptoms escalated or imaging showed new occlusion). Then one of the worsening factors (subsections 8(5)-(9)) must be satisfied and related to service. The "inability to obtain appropriate clinical management" factor is a last resort; the claimant should show that service prevented or delayed treatment (e.g., deployment to a remote area without vascular surgery capability).

For decision-makers, compliance requires checking each element: the diagnosis, the factor existence, the relationship to service, and the correct application of the onset/worsening distinction. The decision-maker must request clarification from the claimant if evidence is insufficient, especially regarding MET intensities or continuous periods of activity. The instrument should be applied mechanically: if a factor is met, the hypothesis is raised; if not, the claim fails unless another SoP applies or the claim is assessed under the balance of probabilities standard.

Medical practitioners advising claimants should document all details of physical activity, trauma history, and imaging findings in their reports, explicitly referencing the SoP thresholds. Failure to do so can lead to delays and adverse decisions.